Ticket Dater Dies were brass inserts that went into a ticket dater. When the dater was used the information on the die would be transferred onto the ticket through an ink strip. Ticket Dater Dies typically include the railroad name, the station where it was used, and often a number for the ticket window as well. Ticket Dater Dies also have 3 holes in them where the numbers for the date could be set so that they could be updated for the date every day.
These dies are very collectable and come up to auction fairly often. They can start under $100 and go up from there. There are some fake dies out there, but generally the best way to check these is to know what authentic dies look like. In use, they were stamped repeatedly and they should show some wear and patina, if they look too clean or the edges don’t look like they’ve seen much use you should be suspicious.